feat: expose concurrency limits and inflight resolves

[alepane21]

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Checklist

• I have discussed my proposed changes in an issue and have received approval to proceed.
• I have followed the coding standards of the project.
• Tests or benchmarks have been added or updated.

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📝 Walkthrough

Walkthrough

Adds two exported Resolver methods exposing semaphore capacity and in-flight resolves, and instruments GraphQLResolveInfo with timestamps and durations for the resolve/render and client-write phases; instrumentation is applied in both normal and singleflight response paths.

Changes

Resolver Concurrency & Timing

Layer / File(s)	Summary
Concurrency getter methods and tests v2/pkg/engine/resolve/resolve.go, v2/pkg/engine/resolve/resolve_test.go	Adds MaxConcurrentResolves() and InflightResolves() to report semaphore capacity and current in-flight resolves; includes TestResolver_ConcurrencyGetters verifying state transitions.
Response resolve/write timing instrumentation v2/pkg/engine/resolve/resolve.go	Extends GraphQLResolveInfo with ResponseResolveStartTime, ResponseResolveDuration, ResponseWriteStartTime, and ResponseWriteDuration; records start times and durations around resolvable.Resolve(...) and writer.Write(...) in both ResolveGraphQLResponse and ArenaResolveGraphQLResponse (including singleflight follower path).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description only contains the repository's contribution template without any substantive details about the changes, rationale, or implementation approach.	Provide a meaningful description of the changes, including the motivation, what concurrency metrics are exposed, and why they are useful for users.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: exposing concurrency limits and inflight resolver statistics through new public methods.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ale/eng-9608-dns-lookup-timeout-impacting-wundergraph-router-latency

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@v2/pkg/engine/resolve/resolve.go`:
- Around line 390-394: The current path sets resp.ResponseResolveStartTime and
resp.ResponseResolveDuration after calling t.resolvable.Resolve but leaves
resp.ResponseWriteStartTime and resp.ResponseWriteDuration zero; update
ResolveGraphQLResponse so that immediately after computing responseResolveStart
and resp.ResponseResolveDuration you also set resp.ResponseWriteStartTime =
responseResolveStart and resp.ResponseWriteDuration =
resp.ResponseResolveDuration (or compute a separate duration using
time.Since(responseResolveStart) for clarity) so GraphQLResolveInfo is populated
consistently; locate this in the block around t.resolvable.Resolve,
resp.ResponseResolveStartTime, and resp.ResponseResolveDuration.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 7fe681f and 5cd0c14.

📒 Files selected for processing (1)

• v2/pkg/engine/resolve/resolve.go